EM算法。问题背景是，有N条长为L的DNA序列，每条序列里面有一条长尾K的目标序列，但不知道他的位置，目标序列内的核苷酸服从foreground product multinomial distribution，非目标序列服从background

multinomial distribution，改程序意在求解两种分布的参数。-EM algorithm. Background to the issue is that there are N pieces of length L of DNA sequences, each sequence which has a target sequence Nagao K, but do not know his position, the target nucleotide sequence within obedience foreground product multinomial distribution, non-target sequence obey background multinomial distribution, the program is intended to change the parameters in solving the two distributions.